Preparation:

1

Heat 1 tablespoon oil in a large nonstick skillet over medium heat. Add onion and cook until softened, about 3 minutes. Add mushrooms and cook, stirring, until they release their juices, 10 to 12 minutes.

2

Add garlic and thyme and stir until fragrant, about 30 seconds. Add sherry and cook until mostly evaporated, about 3 minutes. Stir in the remaining 1 tablespoon oil, lemon juice, salt and pepper and continue cooking for 1 minute more. Pour over greens in a large bowl and toss to coat. Sprinkle with Parmesan.